How to Fix Audio Out of Sync in Avidemux (Audio Shift Guide)

Q: What Audio Shift value should I use?

There is no universal number — start with a round estimate (±500 ms if speech sounds about half a second off; positive if audio comes first, negative if it lags) and halve the correction until lips match words.

Q: I shifted the audio but it's still out of sync at the end — why?

You have progressive drift, not a fixed offset — typically from variable frame rate sources. Shift moves the whole track by a constant amount and cannot fix a growing delay. Use Resample FPS to unify the frame rate and the audio Stretch filter to match audio length to video.

Q: Why is the delay different in different players?

Some players mis-handle files with unusual timestamps (especially VFR screen captures). Confirm the problem in at least two players before fixing. If only one player shows it, the file is probably fine.

Audio out of sync means the soundtrack no longer lines up with the picture — voices move their lips before or after you hear the words. In Avidemux you fix it with Audio > Shift, which moves the whole audio track forward or backward by a number of milliseconds. The crucial step is diagnosing which kind of delay you have first, because the two kinds need completely different fixes.

Step 1: diagnose — fixed offset or progressive drift?

Symptom	Type	Fix
The delay is the same at the start and the end of the video (e.g. audio is always ~300 ms late).	Fixed offset	Audio > Shift — instant, lossless in Copy mode.
The video starts in sync but drifts further out as it plays — fine at minute 1, noticeably off by minute 20.	Progressive drift	Shift cannot fix this. It is a frame-rate/timestamp problem — see the drift fix below.

Test it: jump to the beginning, note the delay, then jump near the end and check again. Same delay both times? Fixed offset. Growing delay? Drift.

Fix a fixed offset with Audio > Shift

Open the video in Avidemux.
Go to Audio > Shift.
Set the shift in milliseconds according to this direction table:

What you observe	What it means	Shift value to set
Sound comes before the picture (audio ahead of video)	Audio track is too early	Positive delay (delays the audio, pushing it later)
Sound comes after the picture (audio lags behind video)	Audio track is too late	Negative delay (pulls the audio earlier)

For example, if the audio is about half a second ahead of the picture, set +500 ms. If it lags by about 200 ms, set -200 ms.

Play from a few points in the timeline to confirm the sync holds everywhere.
Save: keep Video Output and Audio Output on Copy — the shift is applied at mux time, so the save is fast and lossless.

Tip: find the right number by trial and error — try a round estimate (e.g. ±250 ms), halve the correction each time, and zero in within two or three tries. Most capture-related offsets are between 100 and 500 ms.

Fix progressive drift (Shift won’t help)

Drift happens when the audio and video clocks run at slightly different speeds — the classic cause is a variable frame rate (VFR) source, such as a screen recording or phone capture, where frame timestamps are uneven. Shifting the whole track cannot fix a delay that keeps growing.

Unify the frame rate: go to Video > Filters and add the Resample FPS filter, setting it to a constant target (usually the file’s nominal rate, e.g. 30 fps). This rebuilds even timestamps and removes the underlying cause. (Note: Resample FPS changes frames, so this step requires Video Output set to an encoder, not Copy.)
Stretch or compress the audio: in the 2.8.x line, Avidemux offers an audio Stretch filter under Audio > Filters. Measure the drift (for example “audio is 2 seconds late after 10 minutes”) and use the stretch factor to speed up or slow down the audio track until it matches the new constant-frame-rate video. Audio > Filters UI details can vary between builds, so treat exact dialog labels as “depends on your build version”.
Verify sync at the start, middle, and end before saving.

Quick rule of thumb: constant offset → Audio > Shift, saved in Copy mode. Growing drift → Resample FPS first, then audio Stretch. Mixing them up is why most “I shifted it but it’s still off” complaints happen.

Frequently asked questions

What Audio Shift value should I use?

There is no universal number — it depends on the file. Start with a round estimate: if speech sounds about half a second off, try ±500 ms (positive if audio comes first, negative if it lags). Play a dialogue scene, then halve the correction until lips match words. Most capture offsets land between 100 and 500 ms.

Does fixing audio sync in Avidemux re-encode the video?

Not for a fixed offset: Audio > Shift is applied at mux time, so you can save with both outputs on Copy — no re-encoding, no quality loss, and it takes seconds. Fixing drift requires the Resample FPS video filter, which does need a video encoder (re-encoding) for that pass.

I shifted the audio but it’s still out of sync at the end — why?

You have progressive drift, not a fixed offset. Drift comes from uneven frame timestamps (typically variable frame rate sources like screen recordings). Shift moves the whole track by a constant amount and can never fix a growing delay — use Resample FPS to unify the frame rate and the audio Stretch filter to match the audio length to the video.

Why is the delay different in different players?

Some players mis-handle files with unusual timestamps or codecs (especially VFR screen captures), showing drift that is not really in the file. Before “fixing” anything, confirm the problem in at least two players — ideally including Avidemux’s own preview. If only one player shows it, the file is probably fine and the player is at fault.